(a) Field of the Invention
The present invention relates to a plasma display panel (PDP). More specifically, the present invention relates to a PDP for improving representation performance of low gray scales and a driving method thereof.
(b) Description of the Related Art
A PDP is a flat display for showing characters or images using plasma generated by gas discharge. PDPs can include pixels numbering more than several million in a matrix format, in which the number of pixels are determined by the size of the PDP. Referring to FIGS. 1 and 2, a PDP structure will now be described.
FIG. 1 shows a partial perspective view of the PDP, and FIG. 2 schematically shows a PDP electrode arrangement.
As shown in FIG. 1, the PDP includes glass substrates 1 and 6 facing each other with a predetermined gap therebetween. Scan electrodes 4 and sustain electrodes 5 in pairs are formed in parallel on glass substrate 1, and scan electrodes 4 and sustain electrodes 5 are covered with dielectric layer 2 and protection film 3. A plurality of address electrodes 8 is formed on glass substrate 6, and address electrodes 8 are covered with insulator layer 7. Barrier ribs 9 are formed on insulator layer 7 between address electrodes 8. Phosphors 10 are formed on the surface of insulator layer 7 and between barrier ribs 9. Glass substrates 1 and 6 face each other with discharge spaces between glass substrates 1 and 6 so that scan electrodes 4 and sustain electrodes 5 can extend over address electrodes 8. Discharge space 11 between address electrode 8 and a crossing part of a pair of scan electrode 4 and sustain electrode 5 forms discharge cell 12, which is schematically indicated.
As shown in FIG. 2, the electrodes of the PDP have an n×m matrix format. The address electrodes A1 to Am are arranged in the column direction, and n scan electrodes Y1 to Yn and n sustain electrodes X1 to Xn are arranged in pairs in the row direction.
A subfield in the PDP driving method includes a reset period, an address period, a sustain period, and an erase period (waveforms within a subfield will be described for ease of description).
In the reset period, states of respective cells are reset so that address operations of the cells may be fluently performed. In the address period (or a scan period or a write period), cells that are turned on and turned off on the panel are selected, and wall charges are accumulated at the turned-on cells (addressed cells.) In the sustain period, a discharge for displaying actual images on the addressed cells is performed. In the erase period, the wall charges on the cells are reduced, and the sustain discharge is terminated.
FIG. 3 shows a conventional PDP driving waveform and a quantity of light emitted by a subfield. As shown in the conventional PDP driving method, a minimum unit of light, that is, light of the subfield with a weight of 1 is represented as the summation of the light generated from the cell selected during the address period, the light generated at the time of a sustain discharge during the sustain period, and the light (which is the initial part of the reset period and is ignorable) during the reset period of the second subfield. In other words, in the period of the first subfield, an address discharge (address light) is generated to form positive ions at the scan electrode in the address period. The voltage at the scan electrode Y is established to be higher than the voltage at the sustain electrode X to apply sustain discharge voltage Vs between the scan electrode Y and the sustain electrode X, thereby performing a sustain discharge (sustain light) in the sustain period.
Next, the minimum unit of light is represented through a reset operation of the reset period of the second subfield. In this instance, the light emitted in the reset period is slightly less, so it is ignorable. The light for representing the second subfield (the weight of 2) is represented through the address discharge (address light) and two sustain discharges (sustain discharge voltage Vs is applied in pairs to the sustain electrode and the scan electrode) in the sustain period.
Therefore, since the minimum unit of light in the conventional PDP driving method includes an address discharge (address light) and a sustain discharge (sustain light), it is restricted in realizing a lower brightness. Further, high Xe is currently used so as to increase emission efficiency, and the magnitude of the unit of light generated by a single sustain discharge is increased, and a much lower minimum unit of light is required to increase the representation performance of the low gray scales in this condition.